The mammae, or breasts, are half-sphere-shaped |glands| that overlie the muscles of the chest, predominently the |pectoralis major|, in an area between the third and sixth |ribs| on each side of the chest. They exist in the male as well as the female, but only in a rudimentary state in the former. The development of breasts usually is the first sign of puberty in girls. Among North American and European girls the development of breasts occurs on average, at the age of 11, but it can be apparent as early as 9 or as late as 13. They reach their full development in early adulthood.
